Programming Linux Games John R. Hall Loki Software, Inc. January 15, 2001 2 Contents Work In Progress i 1 The Anatomy of a Game 1 A Quick Survey of Game Genres . 2 Simulation Games . 2 First Person Shooters . 4 Real-time Strategy Games . 5 Turn-based Strategy Games . 7 Role-playing Games . 7 Puzzle Games . 8 Multi User Dungeons . 9 A Quick Look Under The Hood . 11 The Input Subsystem . 11 The Display Subsystem . 12 The Audio Subsystem . 13 The Network Subsystem . 13 The Update Subsystem . 14 The Game Loop . 15 3 4 CONTENTS 2 Linux Development Tools 17 Programming Editors . 17 vi..................................... 18 Emacs . 19 NEdit . 20 Compiling Programs Under Linux . 21 Using The Make Utility . 23 Creating Makefiles . 24 Error Handling . 28 Working With Libraries . 28 Static Libraries . 28 Shared Libraries . 29 Linux Linker Quirks . 32 Debugging Linux Applications . 33 Compiling For Debugging . 33 The GNU Debugger, gdb . 34 The Data Display Debugger . 40 Bug Tracking . 41 Project Management With CVS . 42 A Brief CVS Tutorial . 43 Other Useful Tools . 49 Rapid Text Searching with grep . 49 Updating Source with diff and patch . 50 3 Linux Gaming APIs 53 Times Have Changed . 53 CONTENTS 5 Graphics APIs . 55 SVGALib . 55 General Graphics Interface, LibGGI . 56 Simple DirectMedia Layer, SDL . 56 ClanLib . 56 OpenGL . 57 Plib . 57 Glide . 58 Xlib . 58 Graphical User Interface Toolkits . 59 GTK+ . 59 Tk.................................... 59 Fltk . 60 Qt .................................... 60 SDL GUI support . 60 Audio APIs . 61 The Open Sound System, OSS . 61 Advanced Linux Sound Architecture, ALSA . 61 The Enlightened Sound Daemon, EsounD . 62 The Open Audio Library, OpenAL . 62 Scripting Libraries . 63 Tcl.................................... 63 Guile and MzScheme . 63 Python and Perl . 64 Networking APIs . 64 6 CONTENTS BSD Sockets . 64 OpenPlay . 65 IPX and SPX . 65 File Handling . 66 libpng and libjpeg . 66 libaudiofile and libsndfile . 66 Ogg Vorbis . 67 The SDL MPEG Library, SMPEG . 67 zlib . 68 4 Mastering SDL 69 Computer Graphics Hardware . 70 The Framebuffer . 71 The SDL Video API . 72 Setting Up The Display . 73 Direct Surface Drawing . 77 Drawing With Blits . 82 Colorkeys And Transparency . 85 Loading Other Image Formats . 89 Alpha Blending . 90 Achieving Smooth Animation With SDL . 95 Input and Event Processing . 105 Processing Mouse Events . 105 Processing Keyboard Events . 110 Joystick Events . 113 Portable Threading Support . 117 CONTENTS 7 SDL Audio Programming . 121 Representing Sound with PCM . 121 Feeding a Sound Card . 124 An Example . 125 Integrating OpenGL with SDL . 135 Penguin Warrior . 139 Creating Graphics . 141 Implementing a Parallaxing Scroller in SDL . 142 A Simple Particle System . 147 Game Timing . 152 To Be Continued... 153 5 Linux Audio Programming 155 Competing APIs . 156 Introducing Multi-Play . 157 Loading Sound Files . 157 Using libsndfile . 158 Other Options . 163 Using the Open Sound System . 163 Reality Check . 168 Squeezing Sound Performance with Direct DMA Access . 171 Playing Sound with ALSA . 181 Sharing the Sound Card with ESD . 187 Building Multi-Play . 192 Environmental Audio with OpenAL . 198 OpenAL Basics . 198 8 CONTENTS Adding Environmental Audio to Penguin Warrior . 204 Implementing Game Music with Ogg Vorbis . 212 Working with Vorbis Files . 213 Adding Music to Penguin Warrior . 216 6 Game Scripting Under Linux 227 A Crash Course in Tcl . 228 Built-in Tcl Commands . 230 Interfacing Tcl With C . 235 Linking Against Tcl . 236 Executing Scripts . 236 Commands And Objects . 240 A Simple Scripting Engine . 241 Designing A Game Script ..